<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        button {
            position: relative;
            margin: 100px auto;
            width: 100px;
            height: 100px;
            outline: none;
            border: none;
            border-radius: 50%;
            background: linear-gradient( 0deg, purple, red);
            box-sizing: 0 0 5px rgba(0, 0, 0, 0.08);
        }
        
        i {
            position: absolute;
            top: 0;
            left: 0;
            width: 100%;
            height: 100%;
            background: linear-gradient(#fff, #fff), linear-gradient(#fff, #fff);
            background-size: 50% 2px, 2px 50%;
            background-repeat: no-repeat;
            background-position: center;
        }
    </style>
</head>

<body>
    <button>
        <i></i>
    </button>
</body>

</html>